The Keys to Oz are six special keys forged in the magical realm of Oz, in intention to serve as a quick and safe way to travel through dimensions, as they have the power turn any ordinary door into a portal to Oz.
Dean first encountered the Key to Oz when he was going through the Men of Letters' inventory and not knowing its purpose, stored it in his room. The Wicked Witch was trapped on Earth and was searching for the Key to bring her armies from Oz and rule over this dimension. Dorothy tells the brothers of the Witch's plan and they race to protect the Key. Dean does find the Key, but the Witch snatches it and escapes. While brewing a potion to serve as a beacon to her minions, she inserts the Key into the keyhole of a non-descript door and Oz is shown on the other side. Charlie later kills the Witch and obtains the Key. When Dorothy returns to Oz with Charlie, she uses the Key to open another door and takes it with her. Charlie later returns to stop her dark side who has broken the Key. According to Clive Dylan, there are six Keys to Oz, and as they are made of Oz steel, they can only be repaired in Oz if broken.